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即使有環回，網路流量也會波動

tag-icon • tag-icon linux-networking ubuntu-12.04 loopback network-traffic iperf
即使有環回，網路流量也會波動

我正在使用 iperf 工具對兩台相同的電腦（Dell Blade Server M620）上的網路介面進行基準測試。兩者都給出了不同的結果。

  • 在第一台機器上，我運行伺服器和客戶端：

伺服器==>iperf -s -B 172.17.250.200

Server listening on TCP port 5001 Binding to local address 172.17.250.200 TCP window size: 85.3 KByte (default) ----------------------------------------

新 shell 上的客戶端==> iperf -c 172.17.250.200 -u -i l -b 250m,

WARNING:interval too small, increasing from 0.00 to 0.5 seconds -----------------------------------------------------------

Client connecting to 172.17.250.200, UDP port 5001
Sending 1470 byte datagrams 
UDP buffer size:  208 KByte (default)
------------------------------------------------------------
[  3] local 172.17.250.200 port 56853 connected with 172.17.250.200 port 5001
[ ID] Interval       Transfer     Bandwidth
[  3]  0.0- 0.5 sec  7.45 MBytes   125 Mbits/sec 
[  3]  0.5- 1.0 sec  7.45 MBytes   125 Mbits/sec
[  3]  1.0- 1.5 sec  7.45 MBytes   125 Mbits/sec
[  3]  1.5- 2.0 sec  7.45 MBytes   125 Mbits/sec
[  3]  2.0- 2.5 sec  7.45 MBytes   125 Mbits/sec
[  3]  2.5- 3.0 sec  7.45 MBytes   125 Mbits/sec
[  3]  3.0- 3.5 sec  7.43 MBytes   125 Mbits/sec
[  3]  3.5- 4.0 sec  7.44 MBytes   125 Mbits/sec
[  3]  4.0- 4.5 sec  7.46 MBytes   125 Mbits/sec
[  3]  4.5- 5.0 sec  7.45 MBytes   125 Mbits/sec
[  3]  5.0- 5.5 sec  7.45 MBytes   125 Mbits/sec
[  3]  5.5- 6.0 sec  7.45 MBytes   125 Mbits/sec
[  3]  6.0- 6.5 sec  7.45 MBytes   125 Mbits/sec
[  3]  6.5- 7.0 sec  7.45 MBytes   125 Mbits/sec
[  3]  7.0- 7.5 sec  7.45 MBytes   125 Mbits/sec
[  3]  7.5- 8.0 sec  7.44 MBytes   125 Mbits/sec
[  3]  8.0- 8.5 sec  7.46 MBytes   125 Mbits/sec
[  3]  8.5- 9.0 sec  7.45 MBytes   125 Mbits/sec
[  3]  9.0- 9.5 sec  7.46 MBytes   125 Mbits/sec
[  3]  9.5-10.0 sec  7.44 MBytes   125 Mbits/sec
[  3]  0.0-10.0 sec   149 MBytes   125 Mbits/sec`

  • 在第二台機器上，我使用相同的配置運行，得到以下結果：

    伺服器==>iperf -s -B 172.17.250.190

    新 shell 上的客戶端==>iperf -c 172.17.250.190 -u -i l -b 250m

    WARNING: interval too small, increasing from 0.00 to 0.5 seconds.
------------------------------------------------------------
Client connecting to 172.17.250.190, UDP port 5001
Sending 1470 byte datagrams
UDP buffer size:  208 KByte (default)
------------------------------------------------------------
[  3] local 172.17.250.190 port 59887 connected with 172.17.250.190 port 5001
[ ID] Interval       Transfer     Bandwidth
[  3]  0.0- 0.5 sec  3.00 MBytes  50.3 Mbits/sec
[  3]  0.5- 1.0 sec  7.45 MBytes   125 Mbits/sec
[  3]  1.0- 1.5 sec  7.45 MBytes   125 Mbits/sec
[  3]  1.5- 2.0 sec  7.45 MBytes   125 Mbits/sec
[  3]  2.0- 2.5 sec  7.05 MBytes   118 Mbits/sec
[  3]  2.5- 3.0 sec  2.95 MBytes  49.5 Mbits/sec
[  3]  3.0- 3.5 sec  2.96 MBytes  49.7 Mbits/sec
[  3]  3.5- 4.0 sec  2.95 MBytes  49.5 Mbits/sec
[  3]  4.0- 4.5 sec  2.97 MBytes  49.8 Mbits/sec
[  3]  4.5- 5.0 sec  2.96 MBytes  49.7 Mbits/sec
[  3]  5.0- 5.5 sec  2.88 MBytes  48.3 Mbits/sec
[  3]  5.5- 6.0 sec  2.88 MBytes  48.3 Mbits/sec
[  3]  6.0- 6.5 sec  2.89 MBytes  48.5 Mbits/sec
[  3]  6.5- 7.0 sec  2.92 MBytes  49.0 Mbits/sec
[  3]  7.0- 7.5 sec  2.94 MBytes  49.3 Mbits/sec
[  3]  7.5- 8.0 sec  2.93 MBytes  49.2 Mbits/sec
[  3]  8.0- 8.5 sec  2.95 MBytes  49.5 Mbits/sec
[  3]  8.5- 9.0 sec  2.95 MBytes  49.5 Mbits/sec
[  3]  9.0- 9.5 sec  2.94 MBytes  49.3 Mbits/sec

為什麼兩台機器結果有差異，它們是相同的機器。一台機器顯示穩定的 125Mbit/sec 流量，另一台機器顯示流量波動。
我還嘗試在兩台機器上使用 iperf 使用 ip 位址“127.0.0.1”，但我仍然面臨類似的問題。在環回的情況下，我認為流量不會通過網卡，但環回仍然存在波動。兩台機器都運行 Ubuntu 12.04 Server 64 位元。任何可能出錯的幫助將不勝感激。

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